1. Field of the Invention
The present invention relates to a kit and a method for detecting denatured lipoproteins, and, more particularly, to a kit and a method for detecting denatured lipoproteins useful for the clinical investigation and diagnosis of abnormal lipid metabolism which can be a cause of heart diseases (e.g. cardiac infarction), diabetes, and various types of atherosclerosis diseases such as cerebrovascular disorders (e.g. cerebral hemorrhage).
2. Description of the Background Art
Abnormal lipid metabolism can be defined as abnormality in either synthesis, secretion, or degradation of lipoproteins. Abnormal lipoprotein metabolism includes congenital abnormality and acquired abnormality.
Abnormal lipid metabolism is considered to be a cause of various diseases such as heart diseases (e.g. cardiac infarction) and various types of atherosclerosis diseases such as cerebrovascular disorders (e.g. cerebral hemorrhage), and to have significant influence on the progress and aftercare of these diseases Detection of abnormal lipid metabolism is thus very important for the clinical investigation and diagnosis of these diseases.
A method most widely accepted for detecting abnormal lipid metabolism is that using the total cholesterol value in blood as a parameter. With this method, the total cholesterol value in blood is measured by a conventional method (e.g, an enzymatic method), and abnormal lipid metabolism is judged to be present if the value falls outside the normal range which was established based on clinical and experiential knowledge In another method used in recent years lipoproteins in blood, i.e., combined lipid-apoproteins, are fractionated by specific gravities, and a cholesterol value for high specific gravity lipoproteins (high density lipoproteins; HDL) is measured. The HDL cholesterol value, or the value obtained by subtracting the HDL cholesterol value from the total cholesterol value (the atherosclerosis index), is used as a parameter for detecting abnormal lipid metabolism.
According to the results of many immunological studies and clinical knowledge accumulated up to the present time, however, these conventional methods of detecting abnormal lipid metabolism do not always exactly reflect the incidence of abnormal lipid metabolism and have only a limited clinical significance. This is because in these methods the total or HDL cholesterol values, which are not necessarily associated with abnormal lipid metabolism, are used. Although the high value of total cholesterol value can be one of the risk factors of ischemic heart diseases [e.g. Med. Clin. North Am., 58, 363-379 (1974)], it does not directly relate to the diseases Occurrence of the diseases in groups with normal lipid metabolism or healthy conditions in groups with highly abnormal lipid metabolism according to these detection methods is not rare. Detection using as a parameter a HDL cholesterol value or using an atherosclerosis index based on the HDL cholesterol value does not always accurately reflect the incidence of disease [Arterial Scherosis, 14, (4), 931-936 (1986)].
Many reports have recently surfaced discussing the significance on actual abnormal lipid metabolism of denatured lipoproteins which are produced when lipoproteins such as very low density lipoproteins (VLDL) undergo certain types of actions in vivo [e.g, Hui, D. Y., Innerarity, T. L. and Mahley, R. W., J. Bio.. Chem., 259, 860-869 (1984); Gonen, et al., Diabetes, 30, 875 (1981)].
Detection of such denatured lipoproteins can therefore more accurately detect the incidence of abnormal lipid metabolism and is thus considered to be clinically very useful as a diagnostic means for determining diseases involving abnormal lipid metabolism, especially for the early discovery of the diseases and for monitoring the progress or curing effects of the diseases. Details of such denatured lipoproteins are, however, not yet elucidated at the present time and there are no known methods for their detection.
The present inventors have conducted extensive studies in order to develop a method and a kit for accurately detecting abnormal lipid metabolism which can detect various diseases involving abnormal lipid metabolism and can monitor the progress or curing effects of such diseases. As a result, the present inventors found that a portion obtained by excluding lipoproteins constituting apoprotein A-I (Apo A-I-containing lipoprotein) and lipoproteins constituting apoprotein B-100 (Apo B-100-containing lipoprotein) from total plasma lipoproteins corresponded to the above denatured lipoproteins. The inventors further found that the Apo A-I-containing lipoprotein and the Apo B-100-containing lipoprotein could be removed when a blood sample was incubated with affinity gels containing specific antibodies, thus ensuring an accurate and ready measurement or detection of the amount of denatured lipoproteins in the sample. Such a finding has led to the completion of the present invention.